The Electrical Impedance Tomography (EIT) allows visualizing and monitoring a cross-section of parts of the human body, by capturing its electrical potential. An electrical current around the surface is conducted inside the body in a rotative pattern, generating a gradient of electrical potential on the surface. The electrical impedance distribution measured in the body parts is transformed, with the help of an image reconstruction algorithm, in a two-dimensional image. For this reason, the EIT has a great potential to be used in the medical field, mainly for image visualization in real-time of the cardiopulmonary functions, for example, in situations in which patients need to be ventilated or have suffered an accident, trauma, etc.
A typical biomedical EIT apparatus utilizes the concept of placing a plurality of equidistantly spaced electrodes, surrounding totally one part of the body. Generally, in the monitoring system it is necessary to precisely place the 16 to 32 electrodes around the desired surface. Since the use of multiple electrodes is needed, it is difficult to precisely place the electrodes one-by-one around the body, mainly in an equidistant form and in the same cross-section. Furthermore, it is a laborious process that requires time, attention and skilled personnel.
A solution for the problem above makes use of an elastic belt with electrodes. The basic idea of the electrode belt is to install a plurality of electrodes in an elastic material. In this way, the placement of the electrodes around a body would be quick and the elastic material would provide equidistant electrodes, at the same time. However, it is difficult to guarantee an equidistant position of the electrodes by using an elastic material. Furthermore, to avoid the electrodes from moving on the body during the data acquisition, this belt has to be tightly placed on the desired surface. Accordingly, this elastic force applied to the surface of the thorax can provoke scabs and make breathing difficult. For an adequate fixation of the belt it is necessary to provide several belt sizes due to, for example, the existence of several thorax perimeters, which generates a high cost inventory and the necessity of a large stock. Another problem is the possibility of occurring bad contact of the electrodes with the external part of the body under observation, due to the existence of different thorax anatomies, which problem cannot be solved by using an elastic material. Such differences occur as a function of the sex and muscular structure of the patient, for example, male patients who have large chest muscles present a depression in the middle of the chest and, similarly, in the middle of the back as a consequence of the muscular structure of the back; in women, there are anatomical variations of the thorax, mainly regarding the different breast sizes.
Situations that require discontinuity in the electrode line around the thorax, or situations that do not allow the electrodes to totally surround the body, cannot be monitored by the current EIT systems, such as, for example, post-operative period of cardiac surgeries, lesions caused by side arms or firearms, burns, skin lesions that result in bloody areas due to dermatological or infectious diseases, or a situation in which there is no access to a part of the body, for example, when the victim is trapped in the accident site or has injured the spinal cord, making difficult or even impeding his/her movement.
Moreover, the present state of the art does not allow optimizing the image resolution and definition in a region of interest. For example, U.S. Patent Application 2004/0260167 A1 describes an electrode elastic belt that can be formed by joining belt segments, the segments presenting the same number of electrodes that can be equally spaced from each other. In accordance with the teachings of the document above, the formation of the electrode belt in multiple interconnected segments connected presents the advantage of reducing the number of electrical conducting cables disposed along the belt, besides leading to a quick and easy application of the electrodes to unconscious patients or that cannot be moved.
Despite the benefits regarding facility of application and reduction of the extension of the conducting cables along the electrode belt, this prior art solution proposes an electrode distribution surrounding totally a body segment, making impossible its use in situations in which the electrode belt has to be interrupted in one or more regions of the body segment.
Due to the constructive form of the electrode elastic belt, it is not possible to provide concentration of electrodes in specific regions, that is, an irregular electrode distribution, aiming at obtaining images with higher definition in certain areas if interest, even in situations in which the electrode belt has to be interrupted in one or more regions of the body segment.